Steven Santini was born on March 7, 1995, in Bronxville, New York. A standout defender in the USHL, he was selected in the second round of the 2013 NHL Entry Draft by the New Jersey Devils and would go on to attend Boston College.

Following his third collegiate season, Santini would choose to forgo his final year of NCAA eligibility and signed with the Devils on April 9, 2016. He made his NHL debut that evening in a 5-1 victory over the Toronto Maple Leafs.

The 2016-17 season would be Santini's first full professional campaign. He would suit up in 38 games for the Devils, scoring twice and adding five assists.

Internationally, Santini helped the United States to a fifth place finish and the 2014 World Junior Championship and to a fourth place finish at the 2016 World Championship.